public Abs()
{
Left = new Node(
$"Abs@{Id}:L",
(self, g, v) =>
{
switch (v)
{
case Int i:
var g2 = g.BindVal(Right, Val.Int(Math.Abs(i.Value)));
return(g2, v);
case Choice c:
var results = c.Values.Select(vv => self(self, g, vv)).ToArray();
throw new NotImplementedException();
case Any _:
return(g, g.GetVal(Left));
public Constant(int value) : this(Val.Int(value))
{
}